Cancer is one of the most dreaded diseases of the 20th century and spreading further with continuance and increasing incidence in 21st century. In the United States, as the leading cause of death, it accounts for 25% of all the deaths in humans presently. It is considered as an adversary of modernization and advanced pattern of socio-cultural life dominated by Western medicine. Multidisciplinary scientific investigations are making best efforts to combat this disease, but the sure-shot, perfect cure is yet to be brought into world of medicine.
Natural anticancer agents are an important area of the current research and are in good demand all over the world. As a result of endless efforts by the scientist around the world, certain lead molecule such as vincristine (VCR), vinblastine (VLB), taxol and camptothecin have been discovered as nature's boon for cancer therapy.
Iridoid glycosides are important natural product and occur in a large number of plant families. Many reviews have dealt with their distribution, structure, properties and biosynthesis (Balachandran, P. Govindarajan, R. Pharmacological Research. 2005, 51, 19; El-Naggar, L. J. Beal, J. L. J. Nat. Prod. 1980, 43, 649). They have been reported to possess various biological activities such as antitumoral (Ishiguru, K.; Yamaki, M.; Takayi, S.; Ikada, Y.; Kawakani, K.; Ito, K.; Nose, T. Chem. Pharm. Bull. 1986, 34, 23) hemodynamic (Circosta, C.; Occhiuto, F.; Ragusa, S.; Trovato, A.; Tumino, G.; Briguglio, F.; De Pasquale, A.; J. Ethnopharmacol. 1984, 11, 259.), cholaratic (Miyagoshi, M.; Amagaya, S.; Ogihara, Y.; J. Pharmabiodyn. 1988, 11, 186), hepatoprotective (Chang, I. M.; Ryu, J. C.; Park, I. C.; Yun, H. S.; Yang, K. H. Drug Chem. Toxicol. 1983, 6, 443), antimicrobial, hypotensive, analgetic, antichloristic, sedative, laxative and various other effects (Sticher, O. (1977) In; New Natural Products and Plant Drugs with Pharmacological, Biological or Therapeutical Activity, (Wagner, H.; Wolff, P.; eds.). 137-176, Springer Verlag, Berlin).
Loganin, an iridoid glycoside is the major constituent of Strychnos nux-vomica fruit pulp. It has long been used as a precursor for the biosynthesis of indole alkaloids and lately it has been reported to posses various pharmacological activities (Graiku, K.; Aligiannis, N.; Chinou, I. B.; Harvala, C. Z. Naturforsch. 2002, 57C, 95; Mathad, V. T.; Raj, K.; Bhaduri, A. P.; Sahai, R.; Puri, A.; Tripathi, L. M.; Srivastava, V. M. L.; Bioorganic & Meidcinal Chemistry, 1998, 6, 605; Visen P. K. S.; Saraswat, B.; Raj, K.; Bhaduri, A. P.; Dubay, M. P.; Phytotherapy Research, 1998, 12, 405; Raj, K.; Matahad , V. T.; Bhaduri, A. P.; Ind. J. Chem., 1996, 35B, 1056; Recio, M. C.; Griner, R. M.; Manez, S.; Rias, J. L. Planta Med., 1994, 60, 232; Tandon, J. S.; Srivastava, V.; Guru, P. Y. J. Nat. Prod. 1991, 54, 1102; Handa S. S.; Sharma, A.; Chakroborti, K. K. Fitoterapia, 1986, 27, 307; Woerdengbag H. J.; Moska T. A.; Pras, N,; Malingre T. M. J. Nat. Prod. 1993, 56, 849. Strychnos Linn. (Fam. Loganiaceae) a large genus of scandent shrub or trees, found throughout the tropic and subtropics. Nearly 20 species occur in India, of which Strchnos nux-vomica renowned for the drug value of its poisonous alkaloids, Strychnine and Brucine. Strchnos nux-vomica is commonly known as Snake-wood or nux-vomica tree (Anonymous, wealth of India, vol X. CSIR, New Delhi, 1961, 62).
Chemical investigations:
On going through the literature it was observed that loganin, a bitter glycoside isolated from Strchnos nux-vomica (Dunstan, W. R.; Short, F. W.; Pharm J Trans, 1983, 14, 1025; Merz, K. W.; Kerbs, K. G.; Arch Pharm, 1937, 275, 217; Meez, K. W.; Lehmann, H.; Arch Pharm, 1957, 290, 543) and other species of strychnos, Menyanthes trifoliate, Lonicera and Hydrangea-species has recently been the subject of various chemical and biosynthetic investigations. In 1974 Bisset et al isolated loganin from the fruit pulp of Strchnos nux-vomica as a major iridoid along with other minor iridoids and alkaloids. In the same year Isiguro et al reported the antitumor activity of several iridoid glycosides and their aglycones. In 1986 Handa et al reported that in traditional system of medicine, an iridoid glycoside (loganin) have a promising protective effect against liver disorders.
In 1991 Tandon et al J. Nat. Prod. 1991, 54, 1102, reported the antileishmanial activity of iridoid glycosides both in vitro (against anastigoles in macrophage cultures) and in vivo (in hamsters) test system. In 1994 Ricio et a.l Planta Med., 1994, 60, 232 studied the structrural considerations on the iridoids as anti-infllammatory agents. In 1996 Raj et al. Ind. J Chem., 1996, 35B, 1056, described synthesis of various loganin analogues and their hepatoprotective evaluation with structural activity relationship. In 1998 Mathad et al. Bioorganic & Meidcinal Chemistry, 1998, 6, 605 studied the immunostimulant activity profile of modified iridoid glycosides prepared from loganin, keto-loganin and arbortristoside A and some structure activity relationship was carried out.
The detailed literature search revealed that loganin is present in fruit pulp of Strchnos nux-vomica in sufficient amount (Bisset, N. G.; Choudhury, A. K. Phytochemistry, 1974, 13) and possesses various important biological activities such as hepatoprotective (Raj, K.; Matahad , V. T.; Bhaduri, A. P.; Ind. J. Chem., 1996, 35B, 1056), immunostimulant, antimicrobial and various other effects (Sticher, O. (1977) In; New Natural Products and Plant Drugs with Pharmacological, Biological or Therapeutical Activity, (Wagner, H.; Wolff, P.; eds.). 137-176, Springer Verlag, Berlin).
It was also recorded that few short report appeared in literature, refrerence may be made to Bisset, N. G.; Choudhury, A. K. Phytochemistry, 1974; Mathad, V. T.; Raj, K.; Bhaduri, A. P.; Sahai, R.; Puri, A.; Tripathi, L. M.; Srivastava, V. M. L.; Bioorganic & Meidcinal Chemistry, 1998, 6, 605 and Raj, K.; Matahad , V. T.; Bhaduri, A. P.; Ind. J. Chem., 1996, 35B,1056, on loganin for their various biological activities but to the best of our knowledge no work on the anticancer activity of loganin and its semi-synthetic analogues have been reported so far. Hence we wish to report the anticancer activities of loganin and its new semi-synthetic analogues against various human cancer cell lines grown in-vitro. Isolation of loganin was cariied out from the fruit pulp of Strychnos nux-vomica. Further chemical transformation of loganin was carried out to prepare various new synthetic analogues. Finally loganin and its various new synthetic analogues were evaluated for their anticancer activity against various human cancer cell lines.